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Petalocrinidae
Discussion
Weller, S., Davidson, A.D., 1896. Petalocrinus mirabilis (n. sp.) and a new American fauna. The Journal of Geology 4 (2), 166173.
Taxonomy
Petalocrinidae was named by Weller and Davidson (1896). It is not extant. Its type is Petalocrinus. It was considered monophyletic by Mao et al. (2015).
It was assigned to Gasterocomacea by Mao et al. (2015).
It was assigned to Gasterocomacea by Mao et al. (2015).
Subtaxa
Synonymy list
| Year | Name and author |
|---|---|
| 1896 | Petalocrinidae Weller and Davidson |
| 2015 | Petalocrinidae Mao et al. |
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If no rank is listed, the taxon is considered an unranked clade in modern classifications. Ranks may be repeated or presented in the wrong order because authors working on different parts of the classification may disagree about how to rank taxa.
Fm. †Petalocrinidae Weller and Davidson 1896
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G. †Eopetalocrinus Li 1993
G. †Sinopetalocrinus Mu and Lin 1987
G. †Spirocrinus Mu and Wu 1974
G. †Vadarocrinus Prokop 1983
Diagnosis
| Reference | Diagnosis | |
|---|---|---|
| Y. Y. Mao et al. 2015 | The Petalocrinidae is a unique crinoid family with each arm being entirely
(or primarily) a single plate. The assumption by all previous authors was that this plate represents the fusion of numerous brachial plates. This assumption is probably correct. However, the alternative hypothesis is that the arm plate is the expansion of a single brachial plate, and this alternative has not been falsified. Arm fragments, especially those of Vadarocrinus, may superficially look like species of Gissocrinus with greatly widened brachials (e.g., G. magnibrachiatus Springer, 1926, pl. 32, figs. 3-6). However, G. magnibrachiatus has axillary brachials with a single bifurcation of the ambulacrum, and their non-axillary brachials contain a single, straight ambulacrum. This contrasts with petalocrinids that have multiple bifurcations on the single arm plate. |